<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=ab, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <!-- 路径后面的hash值可以用来通信 -->
    <!-- 目的a想访问c -->
    <!-- a给c传一个hash值 c收到hash值后  c把hash值传递给b  b将结果放到a的hash值中 -->
    <iframe src="http://localhost:4000/c.html#iloveyou"></iframe>
    <script>
        window.onhashchange = function(){
            console.log(location.hash)
        }
    </script>
</body>
</html>